Diversity

by Stephen Sylvan Willig

  As I write this I am wintering in the high Rockies of Colorado, teaching skiing to youth at Vail. I live at 10,000’ elevation in what the locals call a ‘park’, a broad flat area between mountain ranges.
  It is beautiful, and beautifully forested, but the forest here is not at all like the forest back at my home in Virginia. It is by nature a virtual monoculture of lodgepole pine (Pinus contorta). I could probably walk for an hour from my apartment and not see another species of tree. And because there is only one dominant species of tree the entire forest ecosystem here is much more 'simple', not nearly as diverse or complex as that in Virginia… fewer insect species, fewer bird species, wildflowers, and all of the soil inhabiting fungal and bacterial species that symbiotically help the plant species to exist.
  Most of us living in central Virginia probably take the forest diversity here for granted… numerous species each of oaks, pines, and hickories, as well as all of the other unrelated genera of common trees: e.g.- Nyssa (gums), Acer (maples), Liriodendron (the ubiquitous yellow-poplars). In fact, such diverse ecosystems are a rare thing on Earth outside of the tropics and the oceans. The forests of the southern Appalachians, such as those in southwest Virginia, comprise the most complex temperate forest ecosystem on Earth. In particular, more species of salamanders are found there than anywhere else on the planet. Some Virginia salamanders, the Peaks of Otter salamander (Plethodon hubrichti) for example, have remarkably restricted ranges… P. hubrichti is found high on a couple of mountains in the Blue Ridge near Bedford-- and nowhere else!
  To further add to this diversity those of us who live near the edge of the Blue Ridge, such as Albemarle and Buckingham counties and Lynchburg, inhabit what is termed an ecotone. An ecotone is an area where two distinct ecological communities converge. In our case it is the meeting of the Blue Ridge and the Piedmont communities. Ecotones themselves are unusually diverse, containing species found in both of those individual ecosystems. There are places near my home in western Buckingham County where I can stand and see both table mountain pines, which are typically found in the Blue Ridge, and loblolly pines, which are not usually found outside of the Piedmont. Go one county west and you would be hard pressed to find any loblollies, one east and there are hardly any table mountain pines.

  Of course Virginia as a whole has an unusual diversity of ecosystems as well. From the sea to the mountains, from the bald-cypress stands of the southeast, to the pine forests found in the coastal plain, to the oak-hickory communities common in numerous parts of the state; one could spend several lifetimes getting to know these rich ecosystems.
 What good is diversity? For one thing, the more diverse a community the more able to withstand disturbances it is. Back to the lodgepole pines in Colorado: there is a species of beetle that feeds on these trees that is currently consuming the entire forest, and consequently catastrophically changing the entire ecosystem. In Virginia, though the hemlock wooly adelgid kills all the hemlock trees, at least it leaves the other trees in the forest unharmed, and there is still a bountiful forest standing. (Perhaps there is a parable here for diversity in human communities?)   Unfortunately we can no longer assume this diversity will always be here. Global warming can cause the higher altitude species, like the Peaks of Otter salamander, to become extinct within our lif etime. Invasive species, such as the aforementioned adelgid (a fuzzy looking little Asian insect that sucks the sap out of hemlock trees), are extirpating other components of the ecosystem. Poor forest ‘management’ converts diverse ecosystems to loblolly pine plantations, just as development converts forests to concrete.   Let’s be grateful we in Virginia live in an area of such bountiful complexity, increase our appreciation of it by getting to better know the ecosystem, and do whatever we can to be sure our forests stay diverse and healthy.